(Fwd) Polyacrylamide Discussion....

[Richard G. Allen]

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Richard G. Allen writes:
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Dear Bob (Sojka),

Thanks for your following message in response to Leonard 
Ornstein's comments to your earlier message on PAM's.  I'm 
sure that many readers of SOWACS will benefit.  I will copy 
your response to the SOWACS discussion group.

Rick Allen

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From Dr. Bob Sojka of the USDA-ARS lab at Kimberly, Idaho:
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Some PAM compounds do contain cation impurities.  
However, not all these effects are due to "impurities".  Many 
PAM molecules are engineered to have various functional 
groups substitued more or less isomorphically for the amide 
groups.  These can be acrylic acid, or others, depending on 
the applications and the use of the vast array of PAM
compounds available.  The sodium and potassium added 
(and hence released) in many PAM formulations are the 
result of grafted functional groups that provide dissociation 
and allow for negative charge sites upon dissociation
of the cations.  They are an intentional structural feature and 
not impurities.  The acrylic acid and sodium formate groups 
commonly substitute for up 20 to 50 percent of the amide 
groups in the linear (water soluble) PAMs used for floculation 
processes and erosion control.

Depending on the particular industrial process used to 
synthesize a given specific PAM compound, some can be 
nearly free of residual cations.  In a recent visit to a SNF 
Floerger subsidiary I was encouraged that new processes are 
coming on line that will greatly enhance all aspects of purity, 
including residual cation, heavy metal, and AMD contents.  Of 
course, the purity will likely affect costs, and affordability will 
depend on the applications and the criticality of purity for the 
application.  There are hundreds of individual PAM
compounds, and it is hard to make sweeping statements 
about all of them, and this is really the message that the 
newcomer needs to internalize.  You need to do your 
homework and learn about the class(es) of compounds
and the individual compound you have an interest in.






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